<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<style>
    .parent {
        width: 300px;
        height: 300px;
        border: 1px solid red;
        position: relative;
    }
    
    .sub-parent {
        width: 200px;
        height: 200px;
        border: 1px solid black;
        position: static;
        margin-left: 20px;
    }
    
    .first {
        width: 100px;
        height: 100px;
        border: 1px solid blue;
    }
    
    .second {
        width: 100px;
        height: 100px;
        position: absolute;
        left: 0;
        top: 0;
        border: 2px solid green;
    }
</style>

<body>
    <div class="parent">
        <div class="sub-parent">
            <div class="first"></div>
            <div class="second"></div>
        </div>
    </div>

</body>

</html>